It is known that transesterification reactions are used for producing an ester which is difficult to obtain by conventional methods (synthesis), starting from another ester which however is easily prepared at moderate cost using conventional methods.
The U.S. Pat. No. 2,433,866 describes a transesterification reaction for the purpose of producing furfuryl acrylate. This reaction takes place in the presence of tertiary aluminum butylate, acting as the catalyst, and a polymerization inhibitor, and this reaction results in a mixture of ester and inhibitor which is its main drawback. The polymerization inhibitors are highly toxic products and the esters so obtained cannot be used in many fields such as foodstuffs, pharmaceuticals, cosmetics and the like. In the absence of an inhibitor, this reaction brings about spontaneous cross-linking producing polymers.
Elsewhere, U.S. Pat. No. 3,996,206, French Pat. No. 2,487,838 and other publications (in particular A. Ujhidy et al, "Method for the preparation of fatty-acid sugar esters". Hung. J. Ind. Chem. 1973, 4 (1), 513-32), disclose transesterification methods in the liquid/liquid phase in the presence of an alkaline carbonate, in order to obtain surfactants (the active agents in detergents). These processes are characterized by the transesterification reaction taking place at temperatures between 110.degree. C. and 165.degree. C., in any event higher than 110.degree. C. These preparation procedures suffer from a major drawback in the large energy expenditure required to raise the substances to the necessary temperature. In industrial processes, very high weights of reagents (several tons) are involved and this energy consumption represents one of the primary factors burdening the cost of the new esters being produced. Also, these reactions are restricted to trans certain esters, namely triglycerides, the esters that are produced being heavy esters derived from saccharose with a highly oxygenated molecule.
There are many other esters which are very difficult and costly to produce by means of the conventional methods, but which evince exceedingly interesting properties in many industrial fields (insecticidal, analgesic, aromatic, fire-proofing properties, etc.)
The object of the present invention is to create a novel transesterification reaction which can be carried out at ambient or low temperature so as to require only a negligible expenditure in energy, or no such expense.
Another object of the invention is to provide a transesterification reaction allowing to obtain many types of esters of furan having diverse substituents. In particular the object of the invention is an especially high-performance reaction of transesterification in order to produce esters which incorporate the furan nucleus (furfuryl esters).